1. Field of the Invention
The present invention relates generally to tube and shell type catalytic reactors having a large number of catalyst containing tubes which are supported in a reactor chamber by upper and lower tube support sheets and which contain catalyst pellets for accomplishing a catalytic reaction with a fluid flowing through the catalyst containing tubes. More particularly, the present invention concerns a testing system for measuring differential pressure of the catalyst containing reaction tubes by introducing pressure at a predetermined flow rate into selected tubes and by reading the back-pressure of the tubes through a transmitter. Even more particularly, the present invention concerns methods and apparatus for identifying and recording back-pressure test data of each of the numerous reactor tubes of catalytic reactors both electronically and by computer print-out. The present invention also concerns apparatus enabling back-pressure testing activity for catalyst tubes that are difficult to access due to their location within the reactor and for accommodating and recording the presence of disabled reactor tube positions that exist due to plugging of faulty reactor tubes or when tube positions are used for thermocouples or other sensing devices.
2. Description of the Prior Art
Tube and shell type catalytic reactors are typically of cylindrical configuration, having a cylindrical outer pressure containing wall for containing reaction fluids. Upper and lower tube sheets are typically welded to the upper and lower ends of the outer cylindrical wall or shell, so as to be oriented in parallel relation with one another. Intermediate tube sheets, between the upper and lower tube sheets, may also be mounted to the outer shell in the same manner. The reactor tubes are typically welded to the upper and lower tube sheets at a multiplicity of holes in the tube sheets, so that process fluids may flow from above or below the tube sheets through the passages of the reactor tubes and thus through the catalyst pellets that fill or partially fill the reactor tubes, causing the catalyst to react with the process fluid to provide the desired reaction and yield a desired fluid product. Tube and shell type catalytic reactors also have upper and lower domed closures that are typically removably secured to the cylindrical outer shell by means of a multiplicity of bolts or threaded studs. The upper and lower domed closures are removable to permit the reactor to be serviced, repaired or overhauled. Some catalytic reactors provide man-way openings in the domed closures, thus permitting the reactors to be serviced without removal of the closures. In this case, the reactor closures are of sufficient internal height above the upper tube sheet that a service worker, having removed a man-way closure and entered the reactor via the man-way, is able to stand on the upper tube sheet and accomplish reactor tube cleaning, catalyst replacement and DP testing activities.
From time to time the catalyst pellets within the reactor tubes will become substantially spent and the quality of the reaction thereof with the process fluid will become degraded. By conducting periodic tests of the reacted product being yielded by reaction with the catalyst of the reactor tubes, a determination can be made to shut down the reactor and overhaul the reactor by removing the spent catalyst from the reactor tubes and replacing the spent catalyst with new catalyst material. After the reactor tubes have been filled with one or more catalyst materials, typically in pellet form, a small quantity of dust is typically present in the reactor tubes along with the catalyst pellets. This dust may interfere with the flow of process fluid through the reactor tubes. Thus it is often desirable to subject the reactor tubes to “blow-down” prior to remove any residual dust prior to subjecting the filled reactor tubes to testing. Reactor tube blow-down is typically accomplished by injecting a high volume of air into the upper ends of the reactor tubes to entrain the dust within the flowing air so that the dust and air exit the lower ends of the reactor tubes below the lower tube sheet of the reactor. The displaced dust is captured and retained by a dust collector and is disposed of in a manner that is safe for personnel and the environment. Reactor tube blow-down is typically done in association with differential pressure testing of the reactor tubes.
To determine the quality of a catalyst loading procedure and to ensure the efficiency of a catalytic reactor process, prior to placing the reactor back in service, some and preferably all of the filled or loaded reactor tubes are tested. The condition of the catalyst loading of the reactor tubes can be detected by measurement of the back pressure of gas, typically air, being forced through the reactor tubes at a predetermined pressure and rate of flow. This test, known as a differential pressure or Delta P or D-P test, will also permit any leaking or otherwise faulty reactor tubes to be detected, so that they can be taken out of service, such as by welding plugs into the upper and lower tube openings. Also, since as mentioned above some of the tube openings may be closed at the upper tube sheet by thermocouples and other temperature, pressure or process sensing devices that have been installed, these non-serviceable reactor tubes are identified as a non-serviceable tube position in the resulting reactor service report. To enable loading of the reactor tubes with catalyst and to conduct D-P tests for filled reactor tubes, personnel will gain access to the upper tube sheet via a man-way in an upper reactor shell member or by removing the upper reactor shell member.
Differential pressure testing of reactor tubes is typically considered necessary or desirable after spent catalyst has been replaced with new catalyst material. If the tubes have been properly filled with catalyst material, each of the multiplicity of reactor tubes will have substantially the same back-pressure when differential pressure testing is accomplished. If any of the reactor tubes are improperly filled, as indicated by excessively high or unusually low back-pressure measurement the catalyst material thereof can be removed and the tube can be refilled. If not properly filled, certain catalyst tubes of the reactor can develop hot spots within the reactor which may cause the process quality of the reactor to degrade earlier than expected or it can cause an improper process reaction to occur, so that the quality of the resulting product can be less than optimum.
In the past, D-P testing of reactor tubes has been done by using a testing device that is capable of testing a single tube and by achieving a differential pressure test that can be visually inspected by the worker conducting the test, but providing no electronic or printed test report for each reactor tube that has been tested. Since present day catalytic reactors may have from 20,000 to 40,000 or even 80,000 reactor tubes it is impractical to test each reactor tube due to the significant labor costs and the length of reactor down time that would be required. Accordingly, it is desirable to provide a mechanism for simultaneously conducting differential pressure testing of a plurality of reactor tubes, for example 8 to 10 tubes or more, to facilitate rapid and simplified reactor tube testing so that all of the reactor tubes of a tube and shell type catalytic reactor can be quickly and efficiently tested in a manner requiring a minimum of labor and a minimum level of technical skill of the worker conducting the test. It is also desirable to provide the test results of differential pressure reactor tube testing in the form of an electronically documented read-out that can be presented in the form of a computer screed display and/or a paper or hard copy, permitting the state of each of the reactor tubes to be individually indicated and a permanent record of the DP test results of each of the multiplicity of reactor tubes to be established and recorded. Further, it is desirable to provide a rather complex reactor tube differential pressure testing system and testing procedure that is simple and efficient for rapid use by relatively unskilled workers and which yields quality test results with minimum time and costs for achieving testing of each of the filled reactor tubes of a reactor. It is also desirable to ensure that testing of each of the multiplicity of reactor tubes is accomplished and that inactive reactor tube positions due to plugged faulty tubes and tube positions having thermocouples or other sensing devices are also specifically identified and recorded as such. It is also desirable to permit filled reactor tube blow-down to be accomplished through the use of the multitube differential pressure testing system and yet enable a higher volume of air to be injected into the reactor tubes to accomplish efficient removal of dust and other debris during blow-down as compared with the volume of air used for differential pressure testing.
2. Description of the Prior Arts
Various apparatus for differential pressure testing of the filled reactor tubes of tube and shell type catalytic reactors has been developed and utilized. Early on, manual reactor tube testing apparatus was developed and utilized that permits manual selection and differential pressure testing to be accomplished, one tube at a time. Thus, with many tube and shell type catalytic reactors having as many as 20,000 reactor tubes and some reactors having from 40,000 to 80,000 reactor tubes, this manual testing apparatus is typically utilized by randomly selecting and testing some of the reactor tubes after all of the tubes have been filled with catalyst material. This single tube testing apparatus presents some test data in the form of a visual back pressure indication, but does not provide any sort of electronic read-out or computer print-out that can be inspected and maintained as a record. This single tube testing apparatus is typically composed of interconnected pipe sections having a lower resilient seal element for sealing its lower end with a selected reactor tube opening. The lower section of the apparatus functions as an air supply through which air is injected into the selected reactor tube. A pressure regulator is mounted to the piping to regulate air pressure being delivered to the unit via a supply hose that is connected to the piping by a quick-disconnect fitting, with the air supply being controlled by a simple on-off valve. A pressure gauge is provided in the piping to visually indicate the air pressure being supplied and a differential pressure monitor is also mounted to the unit for visual inspection of measured back-pressure by the person using the apparatus and being coupled by a tube to the piping at a point below an orifice element. To enable the tapered lower resilient seal element of the unit to establish sealing engagement with a selected reactor tube opening of the upper tube sheet, a lateral pipe section is provided which is engaged by the foot of the user to permit sufficient downward manual force to be applied to deform the tapered lower resilient element against the upper end of the selected reactor tube within a reactor tube opening to effect sealing thereof with the upper end of a reactor tube. With the reactor tube seal being maintained by this foot actuated force, the user will then actuate a valve control lever moving the valve to its open condition to admit regulated gas pressure into the reactor tube. The worker will then read the test data indicia that is present on the back-pressure gauge. Typically, no record of the test data is kept. The user merely arrives at a conclusion, based on random back-pressure tests, concerning the overall accuracy of the tube cleaning and replacement catalyst loading procedure. If the back-pressure of a reactor tube clearly indicates improper reactor tube loading, the user will often make a mark on the upper tube sheet or place a colored marker on a reactor tube opening indicating that the improperly loaded reactor tube must be emptied of catalyst pellets and again filled and tested. Using this method of testing, it is clear that a number of improperly filled catalyst tubes may not be tested and thus the overall integrity of the reactor servicing operation may be less than optimal.
More recently, multi-tube blow-down and D-P testing devices have been developed as indicated by U.S. Pat. No. 6,694,802 of Comardo, which covers a predecessor to the present invention and is identified above as a related patent, and U.S. Pat. No. 6,725,706 of Johns, et al. These multi-tube D-P testing devices have provided reactor owners and service personnel with the capability of mechanized testing of reactor tubes and the capability of achieving test reports in the form of electronic data or hard copies that identify the test parameters of individual tubes (Comardo) or groups of tubes (Johns, et al.). Both of these catalyst tube blow-down and Delta P or back-pressure testing systems are based on the need for efficiency of catalyst tube testing, and the testing of each of the multitude of reactor tubes of a typical tube and shell type catalytic reactor. The multi-tube blow-down and D-P testing apparatus covered by U.S. Pat. No. 6,694,802 Comardo achieves individual testing of each reactor tube and thus provides a test report providing the actual test results of each tube. The apparatus of Johns, et al. conducts simultaneous tests on groups of reactor tubes and thus achieves averaging of the back-pressure for the tubes of each test group. Thus some tubes may test high and others may test low, with the averaged and recorded test measurement perhaps indicating an optimum back-pressure, indicating optimum reactor tube loading, when such may not be the case.